[4] The type series, collected from Mount Kinangop, consists of one male measuring 26 mm (1.0 in) and four females measuring 29–34 mm (1.1–1.3 in) in snout–vent length.

[2] Males are reported to vary in SVL between 25 and 38 mm (0.98 and 1.50 in), making them medium to large sized among Hyperolius frogs.

A dark brown canthal stripe runs from behind the eye to shoulder or groin.

Males have yellow to white throat, or green in green-backed specimens.

[4] Hyperolius montanus is an adaptable species that lives in montane grassland and farmland, montane rainforest, and moor land at elevations of approximately 1,800–3,100 m (5,900–10,200 ft) asl.